1. Field of the Invention
The invention is directed to an improved fuel injection device for an internal combustion engine.
2. Description of the Prior Art
A fuel injection device, known from DE 199 41 770 A1, has a high-pressure pump that supplies highly pressurized fuel into at least one high-pressure reservoir connected to injectors disposed in cylinders of the engine. The injectors are connected to a common return line, which constitutes a low-pressure reservoir. A minimum pressure must be maintained in the low-pressure reservoir in order to assure the proper functioning of the injectors, particularly if they have a control valve with a piezoelectric actuator and a hydraulic pressure booster device.
The fuel injection device according to the invention has the advantage over the prior art that the pressure holding valve permits a minimum pressure to be maintained in the low-pressure reservoir. In addition, it is also possible to fill the low-pressure reservoir with fuel specifically by diverting fuel from the high-pressure reservoir by means of the pressure regulating valve, without requiring an additional fuel-supply pump. The fuel diverted from the high-pressure reservoir is heated in the course of this, which quickly brings the injectors to their operating temperature and stabilizes their operation.
Other advantageous embodiments and modifications of the fuel injection device according to the invention are disclosed. In a simple manner, one embodiment permits the diversion connection to be switched between the low-pressure reservoir and the relief region, which makes it possible to avoid excessively intense heating of the injectors. Another embodiment permits a pressure increase in the low-pressure reservoir during starting of the engine and thus makes it possible for the engine to start reliably.